1. Field of the Invention
The present invention relates to a viewfinder device and to an optical apparatus using the viewfinder device, which is adapted for a small-sized camera of the kind having a solid-state image sensor, such as a digital still camera or a video movie camera, etc.
2. Description of Related Art
The optical apparatuses, such as digital color cameras, are arranged to expose a solid-state image sensor, such as a CCD or CMOS sensor, to light of an object image for a desired period of time in response to a pushing operation on a release button, to convert an image signal which represents a still image of one picture plane obtained by the exposure into a digital image signal, and to obtain an image signal of a prescribed format by subjecting the digital image signal to a process such as a YC process. Digital image signals indicating images picked up and obtained in this manner are recorded in a semiconductor memory one by one. The image signals thus recorded are read out and reproduced in such a signal form that can be displayed or printed. The reproduced signals are then outputted to be displayed on a monitor or the like.
Since a small-sized solid-state image sensor is used for the digital color camera, the use of it facilitates reduction in thickness of the camera. According to the arrangement disclosed in Japanese Laid-Open Patent Application No. Hei 10-126658, camera functions of varied kinds are stored in a card-shaped storage of the size of PC card. This storage is arranged to be accessible by such an external information processing apparatus represented typically by a personal computer by inserting it into a card slot provided in the external information processing apparatus. There is also disclosed the arrangement for providing the camera with a folding-type viewfinder device.
The arrangement of the viewfinder device disclosed in Japanese Laid-Open Patent Application No. Hei 10-126658, however, necessitates some moving parts as a viewfinder optical path is arranged to be formed only when the folding-type viewfinder device is to be used. The arrangement, therefore, tends to result in a complex structure of the camera. Besides, the viewfinder device must be folded every time the camera is to be inserted into the card slot of the external information processing apparatus.
Viewfinders of varied kinds have heretofore been used for small-sized cameras, including an inverted Galilean viewfinder, an Albada viewfinder, a mark viewfinder, a real image viewfinder, etc.
However, each of the viewfinders conventionally adapted for small-sized cameras respectively have some problems, and none of them have been sufficiently satisfactory.
For example, the inverted Galilean viewfinder gives a vague contour of a viewfinder field although its structural arrangement is simple.
The Albada viewfinder and the mark viewfinder give a dark field (viewfinder image) because of use of a half-mirror disposed in the optical path of the viewfinder.
Each of the inverted Galilean viewfinder, the Albada viewfinder and the mark viewfinder is composed of a lens system which is close to an afocal system. The viewfinder, therefore, cannot be formed with one thin lens as it must be formed by arranging at least two lenses away from each other. Reduction in thickness of the viewfinder is, therefore, hardly possible.
The real image type viewfinder gives clear contour of a viewfinder field. However, it necessitates use of a Porro prism besides the use of a plurality of objective lenses and eyepieces. The structural arrangement of the viewfinder of this type is, therefore, complex.
These problems have made it difficult to arrange a viewfinder device apposite to a small-sized camera in such a way as to have a simple structure and yet to give a bright field with a clear contour of the field.